Among already known on-vehicle cameras capable of simultaneously viewing both the right and left directions, there is an imaging apparatus wherein images in both the right and left directions are arranged and taken on the same imaging plane with one or two prisms provided in front of an imaging lens (see Patent Publications 1 and 2).
Among already known small-format imaging optical systems capable of producing less distorted images at wide angles of view, on the other hand, there is a prism optical system that, as set forth in Patent Publication 3 or the like, comprises a first surface having transmission, a second surface having reflection plus transmission and a third surface having reflection, wherein at least the surface having reflection is constructed of a rotationally asymmetric plane.
[Patent Publication 1]
JP(A) 2000-89301
[Patent Publication 2]
JP(A) 2004-341509
[Patent Publication 3]
JP(A) 10-307260
With the conventional imaging apparatus capable of taking images in both the right and left directions with a prism provided in front of the imaging lens, however, the angles of view in the right and left directions become inevitably narrow because the angle of view of the imaging lens is divided into two equal parts: one for taking images in the left direction and another for taking images in the right direction. The resolving power depends on the imaging lens; trying to increase the resolving power around the angle of view unavoidably makes the imaging lens structurally complicated.